the Halogens, Nitrogen, Sulphur and Oxygen. 379 



current of moist oxygen commenced to burn without any puff. 

 It was allowed to cool until black on the outside and the gas 

 in the tube was replaced by air. When the oxygen was turned 

 on again the coal began to glow and in four or five seconds 

 there was an explosion accompanied by a distinct click, flame 

 passing from the coal through the tube for a distance of 

 40 centimeters. The experiment was repeated a number 

 of times. If the oxygen was turned on when the charcoal 

 was incandescent on the outside there was no puff and no 

 flame passed along the tube. A soft porous charcoal gave no 

 puffs. 



Experiment lip. — The glass tube shown in fig. 2 contained 

 charcoal at b which was kept hot during the experiment. At 

 a was a piece of dense wood charcoal a centimeter thick and 

 three long. The two pieces were 40 cm apart. Oxygen not 

 dried was supplied through the small tube. When the char- 

 coal at a was first heated it took fire without any puff. The 

 oxygen was then turned off and as soon as the coal at a ceased 

 to glow air was passed into the tube to displace the gas in it. 

 On turning on the oxygen again the charcoal at a commenced 

 to glow and the charcoal at b burned brilliantly, showing that 

 the other piece had not consumed all the oxygen. After a few 

 seconds there was a slight explosion. The experiment was 

 repeated many times until the piece at a was mostly consumed. 

 The flame accompanying the explosions usually passed from a 

 to b, but sometimes it passed from b to a. 



In 12 the amount of hydrogen and water present was very 

 small and the explosive mixture of gases may be regarded as 

 consisting of oxygen and carbonic oxide and possibly some 

 carbon dioxide. When the charcoal was glowing feebly car- 

 bonic oxide was formed and together with oxygen passed 

 beyond the coal and when the temperature of the burning 

 coal reached the point of ignition of carbonic oxide there was 

 an explosion, and the coal then burned with a flame. In 13 

 and lip the gas was used moist and the charcoal also yielded 

 water when burned. But in these experiments the slow oxida- 

 tion in presence of an excess of oxygen yielded a combustible 

 gas that required a higher temperature than that of feebly 

 burning charcoal to ignite it. 



Am. Jour. Sci.— Third Series, Vol. XLV, No. 269.— Mat, 1893. 

 27 



